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Subject: Re: [PATCH v2] ext4: fix infinite loop when replaying fast_commit
To: "Luis Henriques (SUSE)" <luis.henriques@linux.dev>
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
 Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger@dilger.ca>,
 Harshad Shirwadkar <harshadshirwadkar@gmail.com>
References: <20240515082857.32730-1-luis.henriques@linux.dev>
From: Zhang Yi <yi.zhang@huaweicloud.com>
Message-ID: <1761896f-ce12-9aeb-616d-8451b1436943@huaweicloud.com>
Date: Wed, 15 May 2024 20:27:54 +0800
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On 2024/5/15 16:28, Luis Henriques (SUSE) wrote:
> When doing fast_commit replay an infinite loop may occur due to an
> uninitialized extent_status struct.  ext4_ext_determine_insert_hole() does
> not detect the replay and calls ext4_es_find_extent_range(), which will
> return immediately without initializing the 'es' variable.
> 
> Because 'es' contains garbage, an integer overflow may happen causing an
> infinite loop in this function, easily reproducible using fstest generic/039.
> 
> This commit fixes this issue by unconditionally initializing the structure
> in function ext4_es_find_extent_range().
> 
> Thanks to Zhang Yi, for figuring out the real problem!
> 
> Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
> Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>

Thanks for fixing this issue，looks good to me.

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>

> ---
>  fs/ext4/extents_status.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4a00e2f019d9..3a53dbb85e15 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
>  			       ext4_lblk_t lblk, ext4_lblk_t end,
>  			       struct extent_status *es)
>  {
> +	es->es_lblk = es->es_len = es->es_pblk = 0;
> +
>  	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
>  		return;
>  
>